Loading

Module 1: Solar and Wind Energy

Note di Apprendimento
Study Reminders
Support
Text Version

Principles of Wind Power Systems

Set your study reminders

We will email you at these times to remind you to study.
  • Monday

    -

    7am

    +

    Tuesday

    -

    7am

    +

    Wednesday

    -

    7am

    +

    Thursday

    -

    7am

    +

    Friday

    -

    7am

    +

    Saturday

    -

    7am

    +

    Sunday

    -

    7am

    +

Hi friends, now we will start discussion on the topic wind energy that is the second partof wind energy.The content of today’s class is parts of windmills, the horizontal axis windmill andvertical axis windmill, rotors of windmills, advantage and disadvantage of windmill, windenergy in India and future of wind energy.Now we will see the important parts of horizontal axis windmill and their role.So this slide shows us some example of horizontal axis windmill and different parts.We see here 1 that is blades, 2 is our rotor, 3 is the pitch, 4 is our brake, 5 we haveshaft that is your low speed shaft, this 6 is our gearbox, 7 is our generator, then wehave 8 is control unit and controller, 9 is your anemometer, 10 is your wind vane, then11 is your nacelle, then 12 is our another shaft that is high speed shaft, then 13 isour yaw drive, 14 yaw motor, and 15 our tower.This figure shows us different important parts of the horizontal axis windmill.Now we will see the role of these parts.So let us see the blades number 1.So blade is the sails basically, it captures the kinetic energy of the wind and then itmoves.Then 2 is rotor, rotor fixes the blades with it and also it is attached with the centralshaft.This shaft is attached with one generator, so this socket arrangement is there.This 3 is pitch.The pitch is used to direct the blades in such a way that it will get maximum amountof wind.So we see the rotor brakes, we have some rotor brakes here, so this 4 the rotor brakes, therole is to prevent it from very high speed of the axis.So rotor brakes control over speed and provide parking and emergency braking.So these brakes can be mounted on the rotor or low speed shaft on the generator that ishigh speed shaft.So this is our low speed shaft or it may be high speed shaft or may be in both, so thatway the brakes can work.Then we see low-speed shaft.So low-speed shaft here it is attached with the rotor and then other side it is gettingconnected to one generator, but generator will be of high speed.So this shaft connected to generator will be getting more speed because the diameterhas been reduced here in the socket, the diameter has been reduced here, so the generator shaftgets more rpm, so more electricity can be produced.Then the wind turbine shaft is connected to the center of the rotor, when the rotor spins,the shaft spins as well, in this way the rotor transfers its mechanical rotational energyto the shaft which enters an electrical generator on the other end.Then hub, the hub is important because it gives connection to low-speed shaft as wellas the blades of the rotor, so rotor blades and shaft gets connected with the hub.Then anemometer is a device used for measuring the wind speed.Wind vane, wind vane that we are talking about this always gives the direction of wind andthis at the bottom is attached to it this control unit that control unit gives the signalto the nacelle to move it according to the wind speed, so the total arrangement movesin such a way that maximum wind can be can be used.Then the nacelle is a cover housing that houses all the generating components in a wind turbineincluding the generator, gearbox, drive train and brake assembly.The yaw drive, this yaw drive is an important component of the horizontal axis wind turbines’yaw system and the to ensure the wind turbine is producing the maximal amount of electricalenergy at all times, the yaw drive is used to keep the rotor facing into the wind asthe wind direction changes.So when the wind direction changes, so this according to direction of the wind, the totalnacelle will move in that direction and this yaw drive will help for this movement.So these are the different parts of the horizontal axis windmills.So this yaw drive helps to move the blade and then this controller this wind vane helpsto decide in which directions this movement should be and this control unit perform thisjob by its control mechanism.Now we will see important parts of vertical axis windmill and their role.So this figure shows a vertical axis windmill.So here our one shaft and then here we have 2 hubs, lower hub and upper hub.So in this hub, the shaft is attached and the blades are also attached.So both side we have hub to attach the blades unlike in a horizontal axis one side we hadhub.So then we have guide wire, so guide wire, we have hub, we have rotor, we have rotorhere, we have blades these are the blades, we have shaft.Then we have brake arrangement here, and we have gear and generator and base, this isour base.So these are the different parts of the vertical axis windmill.We see the guide wire.The vertical axis wind turbine normally needs guide wire to keep the rotor shaft in a fixedposition and maximized possible mechanical vibration.Hub already we have discussed.Rotor also we have discussed.The shaft it is connected to the turbine one end and other end it is to the rotor.So the shaft is the part that gets turned by the turbine blades.It in turn is connected to a generator within the main housing.Then the blades, as you have seen the blades are like this, it is not similar to that ofthe horizontal axis turbines.So these blades may be of 2 types, one is may be of savonius wind turbine and that isdrag force type blade and another is lift force type blades that is called Darrieusand giromill wind turbine.Braking, already we have discussed that it can reduce the high speed of the shaft aswell as it can also stop when there is no wind.So the breaking of a small wind turbine can also be done by dumping energy from the generatorinto resistor bank and converting the kinetic energy of the turbine rotation into heat.So this method is useful if the kinetic load on the generator is suddenly reduced or istoo small to keep the turbine speed within this allowed limit, just we are talking about.Then cyclically braking causes the blades to slow down, so which increases the stallingeffect reducing the efficiency of the blades.So this is the role of the braking, so cyclic braking is also not desirable.The gearbox we know that to control the speed of the shaft.The main function of the gearbox is to take low rotational speed from shaft and increasethe rotational speed of the generator.They are made up of aluminum alloys, stainless steel, and cast iron.Base, the base is the roof or building on which it is installed.As you know, the height required for these machines is less than that of the horizontalaxis machines.Now we will see the rotor part.So rotor of wind machines, so horizontal axis and vertical axis.If we see the rotor of these, basically the blades which are attached to these 2 typesof machines are different, in case of horizontal we will get multi-blade and we can get propellertype and vertical axis we can get savonius type or Darrieus type.So this is one example of multi-blade type rotor.You see this is our rotor hub and the blades are connected here.So blade if you see the number of blades are connected in the hub around 12 to 20 numberof blades are attached and other part is also connected with a circular rim.So this is our circular rim connected, and the blade if we see the width also increasesas you go outside.So this is the structure of the multi-blade type rotor and this rotor was previously usedin ancient mills and basically that mills are used for the pumping purpose.So in this type of rotor when we are having these shafts there and then at the bottomof this mill, it is also having one water pump.So we will see this is the case, so we have some multi-blade type rotor here and the multiblades and we see at the bottom it is connected with the pump.So this pump how it is working if we see, so this energy is coming from this machine,so this is lower socket to we are having in a gearbox so we are having the gear, so thisgear diameter is more, and so rpm will be less here, and this is connected with yourcrankshaft, so that this crankshaft arrangement will help to give some vertical movement ofthe pump rod.So that way it helps, it will helps to get the water out from these and for pumping purpose.So that was the initial application of this multiple blade type rotor.As you see the transmission system consists of a power shaft, a speed reducing gear drive,a crank shaft connecting rod mechanism and a pump rod.So the gear drive reduces the horizontal speed by a factor of 3 to 4.So this the gear drive, this is the gear which reduces the speed by 3 to 4 times reduction,by a factor of 3 or 4.The rotational motion is then converted into reciprocating motion.The rotational motion is converted to reciprocating motion by the use of this crankshaft, thatwe have discussed now, this mechanism which is connected this shaft.It is helping to give the reciprocating motion and also which in turn connected by meansof the pump rod to the water pump.So pump rod is used to connect the water pump.So this is the mechanism and that was used in the previous days.This tower is usually steel truss construction.It serves the purpose of keeping the rotor and the windmill head at an appropriate heightfrom the ground where the wind speed is adequate.Now propeller type of rotor came later and these are more suitable for the productionof electricity.So in this case, we get 2 or 1 or 3 blades made from glass fiber, reinforced plastic,and the blades have aerofoil sections with a high thickness-to-chord ratio and yielda high lift relative to the drag.So it gives high lift and gives more rpm.The diameter of the rotor usually ranges from 2 meter to 25 meter.The machine is normally used for generating electricity and then capacity is ranging froma fraction of kilowatt to a few hundred kilowatts being available.The main elements of the machine as seen from the outside are the rotor, the nacelle andthe tower.This is basically suitable for obviously the horizontal axis type of turbines, so thisdesign is usually adapted for large capacity machines.In some cases, the diameter is large enough to permit ascent through an internal staircase.This is our for vertical axis type of machines, this type of rotor is used, savonius rotor.So we see here one S type of structure is formed.So it consists essentially of a hollow cylinder approximately elliptical in shape sliced inhalf.The two halves being fixed, so this is one half of hollow cylinder two part, so one connectedhere, this is our rotor, and so these are the blades, so as a whole it is called savoniusrotor.So the torque is produced by the pressure difference between the two sides of the hubfacing the wind.So here the drag force helps to rotate the rotor blades.But in case of Darrieus rotor, this consists of a number of aerofoil, so this one, thisone, this one so when the air is coming here, so there will be some lift, so lift will helpto move the rotor and the blades.So Darrieus type is theoretically just as efficient as the propeller type if wind speedis constant, so its efficiency is better with respect to savonius type and there are fewmajor difficulties in protecting the Darrieus turbine from extreme wind conditions.This is the mechanism you see here.So this will move this direction.So the lift will work in these directions and it will give some movement.Now advantage and disadvantage of the wind power if we see.So it is a renewable source of energy, this is advantage one.Like solar energy wind power systems are non-polluting, no pollution from the wind power.On a small scale, up to few kilowatt system is costly, but on a large scale, cost canbe competitive with other type of energy available, particularly the conventional electricityand lower cost can be achieved by mass production.So these are the advantage of wind, basically it is pollution free.On that that way it is pollution free, but it also creates some noise pollution becausethese systems are noisy in operation, a large unit can be heard many kilometers away andsuitable sites are sparse.Wind velocity is fluctuating in nature, so every time we may not get wind.It requires very large land area, so it has to be available, wind speed has to be available,then only these machines can be applicable for that area.Then wind power systems have relatively high overall weight, obviously the weight is highand then the large area is needed.The present systems are not practically maintenance free or nor reliable.Storms may extremely damage the wind turbine, so we have to take some action for this.Now we see the wind power in India.So, major work carried out by the Centre for Wind Energy Technology, Chennai, establishedin 1998.In India the cost of wind energy varies from 3.6 to 4.10 that is slightly higher than thatof the conventional energy, the coal waste energy or very competitive.There are approximately 10,500 WECS that is wind energy conversion system installed allover the country which are owned by private owners whereas the total numbers of WECS thatis wind energy conversion system owned by the government is approximately 400.So maximum private players are taking role for the development of this wind technologyin the country.This is the wind map.You see all the coastal areas are having the potential to have the wind power harnessing.If we see the energy cost, the cost is also reducing.In 1990, what was the cost here and now it is expected to reduce here at 2020, and thisis our bulk power competitive price band.So this is our competitive price, in this early stage, the wind energy was costlier,but here now it is very competitive and it is expected to be lower in near future.Here also the US prediction of the cost that is, it is expected to reduce by 2030, it isexpected to reduce.When it is at 2010 the price is 100%, it is expected to be around say 60 or 65% at 2030.So this is the wind energy cost reduction prediction in future.These are the future energy expansion, wind energy expansion in India.So northern region, western region, then southern region and others total 60,000 megawatt electricityproduction is expected by 2022.This is the future of wind energy in the country.So, up to this on this subject.Thank you for your patience.